Such methods are already well known in the art, for instance from the European Patent Application EP-A2-0570937. Therein, the groups are formed by first paging each terminal individually to inform it that it is included in a group with a particular dynamic group address and, after having so paged each of the group members, by then addressing the thus formed group by using this dynamic group address.
The use of groups is a well established practice in particular in mobile communication networks wherein they are for instance used as in the known method to establish a group call via the paging message. Such groups and group calls have however a very wide application area that is neither restricted to terminal paging in a strict sense nor to mobile communication networks nor even, for that matter, to networks that use a so called shared transmission medium in general.
Indeed, on the one hand and as explained in detail later on; the paging message might contain control information for assigning to such a group specific access channels so as to reduce the collision probability or for assigning to such a group specific paging channels on which the terminals of a group are to listen in. The latter feature is advantageous in that it allows decreasing the time needed to page a group of terminals as well as reducing the amount of energy required in each of the terminals to listen in on the paging channels. Also, in conventional wired networks such groups might prove to be useful, for instance in implementing Universal Personal Telecommunications or UPT as with groups it is not necessary to pinpoint the exact location of the terminals of the groups when information has to be conveyed thereto.
In view of the above it may be appreciated that the possibility of defining such groups dynamically--as opposed to pre-assigning them to the terminals or to users thereof on their subscription--is extremely advantageous as the use of a large number of pre-assigned addresses can thus be avoided. Furthermore, the definitions of the groups may be adapted to take account of the present state of the network in which the groups are defined as well as of user or terminal mobility.
However, a major drawback of the above known method for forming dynamic groups is that it entails a large amount of signalling traffic to form each group. This signalling traffic furthermore dramatically increases with the number of groups and the number of terminals included therein and thus puts an undue burden on the network in which these groups are formed, particularly but not exclusively when a transmission resource available therein is scarce, such as for instance in mobile communications systems.